﻿/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Velocity4Net.Ctx;
using System.IO;
using Velocity4Net.Errors;
using Velocity4Net.Runtime;
using System.Collections;
using Velocity4Net.Runtime.Logging;

namespace Velocity4Net.App
{
    ///<summary>
    /// <p>
    /// This class provides a separate new-able instance of the
    /// Velocity template engine.  The alternative model for use
    /// is using the Velocity class which employs the singleton
    /// model.
    /// </p>
    /// <p>Velocity will call
    /// the parameter-less init() at the first use of this class
    /// if the init() wasn't explicitly called.  While this will
    /// ensure that Velocity functions, it probably won't
    /// function in the way you intend, so it is strongly recommended that
    /// you call an init() method yourself if you use the default constructor.
    /// </p>
    ///
    /// @version $Id: VelocityEngine.java 894920 2009-12-31 18:35:25Z nbubna $
    ///
    /// </summary>

    public class VelocityEngine : RuntimeConstants
    {
        private RuntimeInstance ri = new RuntimeInstance();

        /**
         *  Init-less CTOR
         */
        public VelocityEngine()
        {
            // do nothing
        }

        /**
         * Construct a VelocityEngine instance with the specified initial properties.
         */
        public VelocityEngine(Dictionary<string,object> p)
        {
            ri.SetProperties(p);
        }

        /**
         *  initialize the Velocity runtime engine, using the default
         *  properties of the Velocity distribution
         */
        public void init()
        {
            ri.Init();
        }


        /**
         * Set a Velocity Runtime property.
         *
         * @param  key
         * @param  value
         */
        public void setProperty(String key, Object value)
        {
            ri.SetProperty(key, value);
        }

        /**
         * Add a Velocity Runtime property.
         *
         * @param  key
         * @param  value
         */
        public void addProperty(String key, Object value)
        {
            ri.AddProperty(key, value);
        }

        /**
         * Clear a Velocity Runtime property.
         *
         * @param key of property to clear
         */
        public void clearProperty(String key)
        {
            ri.clearProperty(key);
        }

        /**
         * Set an entire configuration at once. This is
         * useful in cases where the parent application uses
         * the ExtendedProperties class and the velocity configuration
         * is a subset of the parent application's configuration.
         *
         * @param  configuration
         *
         */
        public void setExtendedProperties(IDictionary configuration)
        {
            //ri.setConfiguration(configuration);
        }

        /**
         *  Get a Velocity Runtime property.
         *
         *  @param key property to retrieve
         *  @return property value or null if the property
         *        not currently set
         */
        public Object getProperty(String key)
        {
            return ri.getProperty(key);
        }

        /**
         *  renders the input string using the context into the output writer.
         *  To be used when a template is dynamically constructed, or want to use
         *  Velocity as a token replacer.
         *
         *  @param context context to use in rendering input string
         *  @param out  Writer in which to render the output
         *  @param logTag  string to be used as the template name for log
         *                 messages in case of error
         *  @param instring input string containing the VTL to be rendered
         *
         *  @return true if successful, false otherwise.  If false, see
         *             Velocity runtime log
         * @throws ParseErrorException The template could not be parsed.
         * @throws MethodInvocationException A method on a context object could not be invoked.
         * @throws ResourceNotFoundException A referenced resource could not be loaded.
         */
        public bool evaluate(IContext context, TextWriter _out,
                                         String logTag, String instring)
        {
            return ri.Evaluate(context, _out, logTag, instring);
        }

        /**
         *  Renders the input stream using the context into the output writer.
         *  To be used when a template is dynamically constructed, or want to
         *  use Velocity as a token replacer.
         *
         *  @param context context to use in rendering input string
         *  @param writer  Writer in which to render the output
         *  @param logTag  string to be used as the template name for log messages
         *                 in case of error
         *  @param instream input stream containing the VTL to be rendered
         *
         *  @return true if successful, false otherwise.  If false, see
         *               Velocity runtime log
         * @throws ParseErrorException
         * @throws MethodInvocationException
         * @throws ResourceNotFoundException
         * @throws IOException
         *  @deprecated Use
         *  {@link #evaluate( Context context, Writer writer,
         *      String logTag, Reader reader ) }
         */
        public bool evaluate(IContext context, TextWriter writer,
                                        String logTag, Stream instream)
        {
            /*
             *  first, parse - convert ParseException if thrown
             */
            StreamReader br = null;
            String encoding = null;

            try
            {
                encoding = ri.GetString(INPUT_ENCODING, ENCODING_DEFAULT);
                br = new StreamReader(instream, Encoding.GetEncoding(encoding));
            }
            catch (Exception uce)
            {
                String msg = "Unsupported input encoding : " + encoding
                    + " for template " + logTag;
                throw new ParseErrorException(msg);
            }

            return evaluate(context, writer, logTag, br);
        }

        /**
         *  Renders the input reader using the context into the output writer.
         *  To be used when a template is dynamically constructed, or want to
         *  use Velocity as a token replacer.
         *
         *  @param context context to use in rendering input string
         *  @param writer  Writer in which to render the output
         *  @param logTag  string to be used as the template name for log messages
         *                 in case of error
         *  @param reader Reader containing the VTL to be rendered
         *
         *  @return true if successful, false otherwise.  If false, see
         *               Velocity runtime log
         * @throws ParseErrorException The template could not be parsed.
         * @throws MethodInvocationException A method on a context object could not be invoked.
         * @throws ResourceNotFoundException A referenced resource could not be loaded.
         *  @since Velocity v1.1
         */
        public bool evaluate(IContext context, TextWriter writer,
                                        String logTag, TextReader reader)
        {
            return ri.Evaluate(context, writer, logTag, reader);
        }


        /**
         * Invokes a currently registered Velocimacro with the params provided
         * and places the rendered stream into the writer.
         * <br>
         * Note : currently only accepts args to the VM if they are in the context.
         *
         * @param vmName name of Velocimacro to call
         * @param logTag string to be used for template name in case of error. if null,
         *               the vmName will be used
         * @param params keys for args used to invoke Velocimacro, in java format
         *               rather than VTL (eg  "foo" or "bar" rather than "$foo" or "$bar")
         * @param context Context object containing data/objects used for rendering.
         * @param writer  Writer for output stream
         * @return true if Velocimacro exists and successfully invoked, false otherwise.
         */
        public bool invokeVelocimacro(String vmName, String logTag,
                                                  String[] _params, IContext context,
                                                  TextWriter writer)
        {
            return ri.InvokeVelocimacro(vmName, logTag, _params, context, writer);
        }

        /**
         *  Merges a template and puts the rendered stream into the writer.
         *  The default encoding that Velocity uses to read template files is defined in
         *  the property input.encoding and defaults to ISO-8859-1.
         *
         *  @param templateName name of template to be used in merge
         *  @param context  filled context to be used in merge
         *  @param  writer  writer to write template into
         *
         *  @return true if successful, false otherwise.  Errors
         *           logged to velocity log.
         * @throws ResourceNotFoundException
         * @throws ParseErrorException
         * @throws MethodInvocationException
         * @deprecated Use
         *  {@link #mergeTemplate( String templateName, String encoding,
         *                Context context, Writer writer )}
         */
        public bool mergeTemplate(String templateName,
                                             IContext context, TextWriter writer)
        {
            return mergeTemplate(templateName, ri.GetString(INPUT_ENCODING, ENCODING_DEFAULT),
                                   context, writer);
        }

        /**
         *  merges a template and puts the rendered stream into the writer
         *
         *  @param templateName name of template to be used in merge
         *  @param encoding encoding used in template
         *  @param context  filled context to be used in merge
         *  @param  writer  writer to write template into
         *
         *  @return true if successful, false otherwise.  Errors
         *           logged to velocity log
         * @throws ResourceNotFoundException
         * @throws ParseErrorException
         * @throws MethodInvocationException
         *  @since Velocity v1.1
         */
        public bool mergeTemplate(String templateName, String encoding,
                                          IContext context, TextWriter writer)
        {
            Template template = ri.GetTemplate(templateName, encoding);

            if (template == null)
            {
                String msg = "VelocityEngine.mergeTemplate() was unable to load template '"
                               + templateName + "'";
                getLog().error(msg);
                throw new ResourceNotFoundException(msg);
            }
            else
            {
                template.Merge(context, writer);
                return true;
            }
        }

        /**
         *  Returns a <code>Template</code> from the Velocity
         *  resource management system.
         *
         * @param name The file name of the desired template.
         * @return     The template.
         * @throws ResourceNotFoundException if template not found
         *          from any available source.
         * @throws ParseErrorException if template cannot be parsed due
         *          to syntax (or other) error.
         */
        public Template getTemplate(String name)
        {
            return ri.getTemplate(name);
        }

        /**
         *  Returns a <code>Template</code> from the Velocity
         *  resource management system.
         *
         * @param name The file name of the desired template.
         * @param encoding The character encoding to use for the template.
         * @return     The template.
         * @throws ResourceNotFoundException if template not found
         *          from any available source.
         * @throws ParseErrorException if template cannot be parsed due
         *          to syntax (or other) error.
         *  @since Velocity v1.1
         */
        public Template getTemplate(String name, String encoding)
        {
            return ri.GetTemplate(name, encoding);
        }

        /**
         *   Determines if a resource is accessable via the currently
         *   configured resource loaders.
         *   <br><br>
         *   Note that the current implementation will <b>not</b>
         *   change the state of the system in any real way - so this
         *   cannot be used to pre-load the resource cache, as the
         *   previous implementation did as a side-effect.
         *   <br><br>
         *   The previous implementation exhibited extreme lazyness and
         *   sloth, and the author has been flogged.
         *
         *   @param resourceName  name of the resource to search for
         *   @return true if found, false otherwise
         *   @since 1.5
         */
        public bool resourceExists(String resourceName)
        {
            return (ri.getLoaderNameForResource(resourceName) != null);
        }

        /**
         * @param resourceName
         * @return True if the template exists.
         * @see #resourceExists(String)
         * @deprecated Use resourceExists(String) instead.
         */
        public bool templateExists(String resourceName)
        {
            return resourceExists(resourceName);
        }


        /**
         * Returns a convenient Log instance that wraps the current LogChute.
         * Use this to log error messages. It has the usual methods you'd expect.
         * @return A log object.
         * @since 1.5
         */
        public Log getLog()
        {
            return ri.getLog();
        }

        /**
         * @param message
         * @deprecated Use getLog() and call warn() on it.
         */
        public void warn(Object message)
        {
            getLog().warn(message);
        }

        /**
         * @param message
         * @deprecated Use getLog() and call warn() on it.
         */
        public void info(Object message)
        {
            getLog().info(message);
        }

        /**
         * @param message
         * @deprecated Use getLog() and call warn() on it.
         */
        public void error(Object message)
        {
            getLog().error(message);
        }

        /**
         * @param message
         * @deprecated Use getLog() and call warn() on it.
         */
        public void debug(Object message)
        {
            getLog().debug(message);
        }

        /**
         *  <p>
         *  Sets an application attribute (which can be any Object) that will be
         *  accessible from any component of the system that gets a
         *  RuntimeServices. This allows communication between the application
         *  environment and custom pluggable components of the Velocity engine,
         *  such as ResourceLoaders and LogChutes.
         *  </p>
         *
         *  <p>
         *  Note that there is no enforcement or rules for the key
         *  used - it is up to the application developer.  However, to
         *  help make the intermixing of components possible, using
         *  the target Class name (e.g. com.foo.bar ) as the key
         *  might help avoid collision.
         *  </p>
         *
         *  @param key object 'name' under which the object is stored
         *  @param value object to store under this key
         */
        public void setApplicationAttribute(Object key, Object value)
        {
            ri.SetApplicationAttribute(key, value);
        }

        /**
         *  <p>
         *  Return an application attribute (which can be any Object)
         *  that was set by the application in order to be accessible from
         *  any component of the system that gets a RuntimeServices.
         *  This allows communication between the application
         *  environment and custom pluggable components of the
         *  Velocity engine, such as ResourceLoaders and LogChutes.
         *  </p>
         *
         *  @param key object 'name' under which the object is stored
         *  @return value object to store under this key
         * @since 1.5
         */
        public Object getApplicationAttribute(Object key)
        {
            return ri.getApplicationAttribute(key);
        }

        /**
         * Remove a directive.
         * @param name name of the directive.
         */
        public void removeDirective(String name)
        {
            ri.removeDirective(name);
        }

        /**
         * Instantiates and loads the directive with some basic checks.
         *
         * @param directiveClass classname of directive to load
         */
        public void loadDirective(String directiveClass)
        {
            ri.loadDirective(directiveClass);
        }
    }

}
